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------------------ 196~ -----
Effect of 2,4-0 and 2,4,5-T on
Water Quality after a Spraying Treatment
JAY S. KRAMMES and DAVID B. WILLETS
Many foothill communities
in southern California s till depend on 10 cal sources for their
major water needs. As the population there continues to soar,
every acre - foot produced of this
high quality water may be used.
To find way s of boosting usable
water yield from brush .,..covered
watersheds, the Pacific Sou t h west Station is conducting studies at the San Dimas Experimental Forest, 1 northeast of Glendora,
California.
ABSTRACT:
Stream pollution has
not resulted
from removing and
chemically spraying vegetation
at
the bottom of Monroe Canyon
on the San Dimas Experimental
Forest.
The riparian zone and
intermediate slopes were handsprayed several
times with a
mixture 0 f
2,4-D and 2,4,5-T
herbicide.
In an~ther
study,
brush on side slopes was
cut
and sprayed. Soil samples taken
the first month after treatment
showed no traces of herbicides.
Rowe found that removing riparian vegetation from the canyon bottom 0 ~ a southern California w ate r she d, and controlling
regrowth with chemicals, increased water y i e 1 d. 2 But what about
the quality of this streamflow? The question is important in view
of reports that use of some chemical sprays next to water sources
had contaminated streams.
Our studies were made on the 875-acre Monroe Canyon
watershed of the San Dimas Experimental Forest. They show that
herbicidal sprays used as part of a vegetation conversion program
to inc rea s e water yield did not impair streamflow quality. We
also found t hat water yield can be increased through the conversion program.
At the time the Monroe Canyon watershed was cleared (19571959), sprouting vegetation was sprayed with a herbicide mixture
1Maintained by the U.S. Forest Service in cooperation with the
California Division of Forestry.
2Rowe , P. B.
Streamflow increases after removing woodlandriparian vegetation
from a southern California watershed.
Jour.
Forestry 61(5):365-370, illus.
1963
of equal parts of 2, 4-D and 2,4" 5-T in diesel oil. During the clearing operations, 88 gallons of herbicide were applied. Sprouts and
other herbaceous vegetation were to be sprayed annually thereafter;
the first maintenance spraying was done in June 1960.
CANYON BOTTOM STREAMFLOW
In cooperation with the .California Department of Water Resources,
we collected each month a series of water ..8.amples at the gaging stations
near the mouth of the study watershed. Samples were analyzed at a
commercial testing laboratory to determine herbicide and diesel oil
content. Rowe had reported no tra-ce of herbicide in a chemical analysis
of the surface streamflow. '- But he found in some samples small traces
of oil used in the spray mixture . The monthly sampling, begun in 1958,
was interrupted when a wildfire destroyed the vegetative cover in July
1960.
.
Before the fire, we had collected water samples only at the gaging stations; After the fire a more intensive system was deemed necessary. Four sampling points were established in Monroe Canyon: (a)
at the stream gaging ,station near the mouth of the watershed; (b) on
the surface water ju.st above the gagings.tation; (c) at a shallow groundwater well (8 feet deep) several hundred feet upstream of the canyon
mouth; and (d) at a shallow groundwater well at the upper end of the
treated area .
. Hand spraying of stump sprouts and other vegetation was resumed
on May 10, 1961. At times of spraying, there was surface streamflow
throughout the entire treated.area. This streamflow increased the possibilities for pollution. In spraying, we were careful to avoid direct
contamination of the stream. We used 45 gallons of herbicide.
Herbicide content of samples taken at the Monroe Canyon sam pUng locations during a five -month period in 1961 was well below the
safe limit of 1 part per million (p. p. m.) (table 1). No traces of the
diesel oil were found.
A high -intensity storm in November 1961 buried all the sampling
sites under debris and later sampling was confined to the gaging station
site.
Hand spraying for maintenance was again carried out during June
1963. Water samples taken at the end of that month ---the last in the
series - -showed no traces of herbicide or diesel oil.
SPRAYING SIDE SLOPES
In another water -yield study in Monore Canyon, we are trying to
convert vegetation on steep side slopes from deep -rooted brush to grass.
Brush was sprayed by helicopter and individual plants were handsprayed
in June 1961. The helicopter spray mixture consisted of 3/4 gallon (3
pounds acid equivalent) each of low volatile esters of 2, 4 - D and 2, 4, 5-T
in 1 gallon of diesel oil and 17 1/2 gallons of water applied in two 10-
gallon amounts, for a total of 20 gallons per acre. As a follow-up
treatment, we handsprayed the brush with a herbicide mixture of 1/2
gallon (2 pounds acid equivalent) each of 2,4 - D and 2,4,5 -T in 1 gallon of diesel oil, and 98 gallons of water.
Table 1. - -Concentrations of 2, 4 - D and 2, 4, 5 -T herbicide in water
samples from Monroe Canyon
Date
sampled
1
Site
Weir
Surface
Well 1
Well 2
- - In parts per million - - - - - May 10, 1961
0.00
May 22, 1961
.00
June 5, 1961
· 05
0.09
0.01
0.01
July 24, 1961
· 03
· 00
July 31, 1961
· 05
.00
· 00
· 00
· 00
. 00
Aug. 28, 1961
· 00
· 00
· 00
Sept. 25, 1961
· 00
.00
· 04
Oct. 30, 1961
· 00
.00
· 01
.00
· 00
· 00
Jan. 29, 1962
· 00
Feb. 26, 1962
· 00
June 20, 1963
· 00
1Riparian zone vegetation was handsprayed during the week
following the May 22, 1961 sampling and just before the June 20,
1963 sampling.
To determine the presence of herbicide, we took several soil
samples from the brush -conversion area. Samples were taken from
the top 3 inches of soil at several elevations on south -facing slopes.
These soils are generally residual and immature, moderate to coarse
textured, and normally mixed with large amounts of fractured rock.
They average less than 3 feet deep, have low water-retention capacity,
and usually have no profile development.
We found neglegible amounts of herbicide in the samples. In
one of the two samples taken 8 days after spraying, we detected a
small amount of herbicide (table 2). But no trace of herbicide was
found in four samples taken a month and a half after initial spraying ..
Between the dates of spraying and the final sampling, no precipitation
occurred. This eliminated the possibility of chemical leaching below
the sampling level in the soil.
Table 2. --Concentration of 2, 4-D and 2,4, 5-T herbicide in Monroe
Canyon soil after helicopter spraying
Date sampled
Elevation
1
Concentration
Feet
In parts per million
June 19, 1961
2, 100
0.00
June 19, 1961
3, 150
· 17
Aug. 28, 1961
2, 140
· 00
Aug. 28, 1961
2, 150
· 00
Aug. 28, 1961
3,175
· 00
Aug. 28, 1961
3,180
· 00
1Initial helicopter spraying was done on June 12, 1961.
Although 2, 4-D and 2,4, 5-T are similar compounds, their herbicidal effects do not endure for the same length of time; 2, 4-D detoxifies
more rapidly than 2,4, 5-T in the soiL Persistence of herbicides in
soil depends on several factors including (a) moisture content of the
soil, (b) soil texture, (c) pH, (d) "soil temperature and extended period
of warm days, and (e) organic matter content 3 .
These five factors also affect growth of soil micro-organisms
which have been credited with decomposing herbicides. Furthermore,
high soil temperatures are known to cause a revolatilization of 2, 4 - D
and 2,4, 5-T. Therefore extended hot seasons become ideal for detoxification of herbicides which revolatilize from the surface soils of the
slope conversion areas.
JAY S. KRAMMES is studying hydrologic
pro-cesses and ways of reducing floods,
erosion, and sediment. A native of Orwigsbllrg, Pa., he holds a bachelor's degree
(1958) in forestry and a master's degree
(1963) in watershed management from Montana State University. Since 1958 he has
been on the research staff of the Pacific
Southwest Station's San Dimas Experimental
Forest, near Glendora, California. DAVID
B. WILLETS, a civil engineering graduate
of Cornell University, has been with the California Department of Water Resources for
24"years. In 19"50 he became chief of the Southern District's water quality section in Los
Angeles.
~~~----------------------~
3 Alexander, Martin. Introduction to soil microbiology. pp. 238 -244.
New York: John Wiley & Sons. Inc. 1961.